Regensburg 2016 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 46: Poster: Wetting, Nano- and Microfluidics

CPP 46.3: Poster

Wednesday, March 9, 2016, 18:15–21:00, Poster B2

Pairs of rigid particles in inertial microfluidics — •Felix Rühle, Christopher Prohm, and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, D-10623 Berlin

We investigate rigid spherical particles in rectangular microchannels under the influence of Poiseuille flow at intermediate Reynolds numbers. It is well known that a single particle shows inertial focussing in this regime [1]. Furthermore, for rectangular channels with sufficiently large aspect ratio only two lateral equilibrium positions exist.

In this contribution we present first results on the behaviour of a particle pair in such a channel thus increasing the complexity of the one-particle system that has already been thoroughly examined [2]. An in-depth understanding of the multi-particle interactions will provide insights into the properties and dynamics of particle chains as well as the formation of so-called microfluidic crystals [3].

The particle pair is placed in the channel with variable axial distance and lateral positions. Inertial migration in the cross section of the channel is quantified by the lift force profile. We determine how it changes due to the presence of a neighboring particle. This helps us to explain the observed passing trajectories, where particles overtake each other, swapping trajectories, and damped oscillations. The latter involve both axial and lateral motion and occur when particles are on opposite sides of the channel centerline.

[1] G. Segré and A. Silberberg, Nature 189, 209 (1961).

[2] C. Prohm and H. Stark, Lab Chip 14, 2115 (2014).

[3] W. Lee et al., PNAS 107, 22413 (2010).